Stator for axial compressors



Feb. 27, 1951 c. A. DAVIS EI'AL STATOR FOR AXIAL COMPRESSORS 4Sheets-Sheet 1 Filed Feb. 10, 1948 1951 c. A. DAVIS ETAL 2,543,355

STATOR FORI AXIAL COMPRESSORS Filed Feb. 10 1948 4 Sheets-Sheet 2 E I 2E %7 E 26 a v 5 Z5 I 26 9 1 I 10 III I l I WW5 "51 WWW 4 MW? JDfWHZAZEYfl/ZL Feb. 27, 1951 c. A. DAVIS ETAL 2,543,355

STATOR FOR AXIAL COMPRESSORS Filed Feb. 10, 1948 4 Sheets-Sheet 4 N Q AN W wmw i atentecl Feb. 27, 195i STATOR FOR AXIAL COMERESSOBSChristopher Ainsworth Davis, Barrow-on-Soar, near Loughborough, JohnHenry Bill, Alvaston, and Frederick William Walton Morley,Astonon-Trent, England, assignors to Rolls-Royce Limited, Derby,England, a British company Application February 10, 1948, Serial No.7,488 In Great Britain February 17, 1947 9 Claims. (Cl. 230-1 33) Thisinvention relates to axial compressors, such as are for example used ingas-turbine engines, and has for an object to provide an improvedconstruction of stator blade and stator casing for axial compressorswhich have advantages from the point of View of lightness, which isimportant in compressors used in aircraft power plants, and of ease ofmanufacture and assembly.

According to this invention an axial-flow compressor stator assemblycomprises a stator casing havin a relatively thin wall, a plurality ofaxially-spaced main internal reinforcing webs each main web extendingcircumferentially around and projecting radially inwardly from the walland each main web being formed with axially-spaced outwardly facingabutment surfaces curved about the axis of said casing, and a pluralityof intermediate internal reinforcing webs there being at least oneintermediate web between each pair of said main webs, each saidintermediate web extending circumferentially around and projectinradially inwardly from said wall and being formed with an inwardlyfacing abutment surface curved about the axis of said casing; and aplurality of stages of stator blading, each stage of stator bladingcomprising a plurality of blades in circumferential assembly supportedand located by a pair of main webs and at least one intermediate web,the blades being formed with axially and circumferentially extendingblade root platforms, which platforms are formed each withinwardly-facing abutment surfaces at its axially-spaced edges to abutsaid outwardly-facing abutment surfaces of the associated pair of mainwebs, and each with at least one outwardly facing abutment surface 50arranged to cooperate with the inwardly-facing abutment surface of theintermediate web between said pair of main webs as to maintain the bladeroot platform in contact with the abutment surfaces on the main webs andto locate the blade against radial and rocking movement.

Preferably the outwardly-facing abutment surfaces of the blade platformsare formed on ribs projecting radially outwardly from the outer surfacesof the platforms and having an axial dimension less than the axialdimension of the platforms. 7

Moreover it is preferred that the main webs be formed with axially andcircumferentially extending flanges having outwardly-facing abutmentsurfaces of the main webs formed at their axially-spaced edges, and thatthe inner surfaces of the main webs and platforms be arranged to providea smooth continuous surface for the outer wall of the working fluidpassage through the compressor.

It will be appreciated that the invention by reducing the contact areabetween the blade platforms and the casing, facilitates accuracy inmachining of the parts and also simplifies assembly.

By providing strengthenin webs on the inner surface of the casing, thewebs and wall are at substantially the same temperature so thatcircumferential thermal stresses due to the provision of reinforcingwebs are avoided. Further since the wall of the casing is thin and thereinforcing webs also provide the means for retainin the'blades, theoverall weight can be reduced as compared with a casing having externalstrengthening webs. Furthermore, the

.external surface can be substantially smoothwhich is an advantage fromthe point of view of cleanliness and appearance.

There will now be described by way of example of this invention an axialcompressor suitable for use with a gas-turbine-engine. For the sake ofclarity only the compressor stator is illustrated, the compressor rotorbeing omitted. he description has reference to the accompany ingdiagrammatic drawings in which Figure 1 is an external View of thecompressor blade, and Figures 6A, 6B, 6C are a diagrammatic illustrationof the junction between the parts of the compressor casing. e Figure '7is a view corresponding to Figure 3 of an alternative arrangement. 7

Referring to the drawings, the compressor stator comprises astator-casing formed in two partslfi and ll and a number of stages ofcompressor stator-blades 12 which are secured in the casing by theirroot-platforms l3.

The platform [3 of each blade is of substantially rectangular formand islocated at the outer end of the blade so that the latter projectsradially inwards from the compressor casing.

The wall I4 of the compressor casing is of rela tively thin section andis provided internally with continuous, circumferential,radially-projecting strengthening webs l5, l6 so that the externalsurface of the casing is substantially free 'from projections andpresents a clean appearance. The webs I5 which alternate with webs [6,have a greater radial extent than the webs It and terminate at theirinner ends in axially-directed flanges I! so that the webs 15 have aT-section. There are thus formed by each pair of webs IS a groove toreceive the blades platforms 13 with a web It projecting of Figure 3inwardly from the base of the groove. In use the webs l5, l6 and wall 14will be at substantially the same temperature whereby thermal stressesdue to the presence of external webs are avoided.

The outward-facing surfaces [8 of th flanges I! are machined to becurved about the axis XX (Figure 1) of the casing and the inwardlyfacing surfaces 19 of the webs 16 are machined to be similarly curved.

The platform l3 of each blade has its axially spaced edges machined toprovide inwardlyfacing surfaces 20 which are curved about the casingaxis XX, the edges being recessed in the thickness of the platform sothat the surfaces Zil are set back from the front face 2| of theplatform and so that the faces 2! of the blades, when the latter areassembled in the easing, conform to the inner surface 22 of the flangesH to provide a smooth internal surface to the compressor casing. Thesurface of the platform remote from the blade is formed intermediate theaxially spaced edges with a rib 23 the outwardly facing surface 24 ofwhich is machined to be curved about the casing axis XX. The radialextent of the rib 23 is such that when the blade is assembled in agroove between the webs IS with the curved surfaces 20 inblade-retaining abutment with the surfaces ll, the surfaces 24 willcooperate with the surfaces [9 on the webs 16. The curved surfaces 18,24 will be clearly seen in the axial end view of the blade illustratedin Figure 5.

The blades 12 are mounted in the casing by sliding them around thegrooves from the division between the parts 10, H with the surfaces 20in engagement with the surfaces 18 and the surfaces 24 in engagementwith the surfaces [9. It will be appreciated that the blades willthereby be retained accurately in position with the blade radial to thecasing axis, whilst accuracy of machining is facilitated owing to thesmall area of the co-operating surfaces.

The platforms I3 of the blades 12 of each stage will abut through theircircumferentially spaced edges so as to form a substantially continuousring.

' It will be seen that a clearance or space is left between the wall [4and the blade platforms I3, and these spaces provide circumferentialpassages which can be used for effecting tapping from the compressor atappropriate stages, for example for anti-surge bleed purposes or forextracting cooling air.

To retain the blades in position in the parts of the casing prior tojointing of the parts ID. If together, there are provided washers 25(Figures 2 and 4) which are accommodated in recesses 26 in the jointingflanges 21 formed on the parts, [9, II, and which engage thecircumferentially-spaced edges of the platforms 13 of the end blades inthe parts. The washers 25 are held in position by bolts 28 which threadinto bushes 29 secured in the casing parts. The edges of the blades withwhich the washers engage are cut back as illustrated at 30 in Figure 5to receive the Washers.

The parts ID, H are secured together by bolts 3| extending throughbosses 32 formed on the exterior of the casing.

It will be seen from Figure 1, that the plane of division between theparts H], H of the easing does not coincide with the diametral planethrough the axis XX of the casing, but is slightly inclined thereto.This is done so that 4 r the edges of the end blade platforms receivedin each stage of the parts are substantially flush with the joint face,whereby damage to the platforms in assembly is avoided and assembly isfacilitated.

The arrangement is more clearly illustrated in Figures 6A, 6B, 60 whichare continuations one of the other in order, and illustrate thedisposition of the end platforms of the stator blades in each of the 11stages of the compressor. It will be appreciated that since the numberof blades in each stage increases from the first stage of the compressorto the eleventh stage and since the diameter of the casing decreases,the chordal dimension of the platforms decreases from stage to stage.Moreover since there are normally an odd number of blades in each stage,the number of blades accommodated in say the part I0 is one greater thanin the part H, so that the platforms l3l of the end blades in casingpart 40 project at each stage by amount approximately equal to onequarter of the chordal dimension beyond the diametral line XX and theplatforms I32 of the end blades in each stage of other part II are setback by approximately one quarter of the chordal dimension from thediametral line.

The joint between the parts H), II indicated in Figures 6A, 6B, 6C istherefore made to lie in a plane which is inclined to the diametralplane and which substantially contains the end surfaces of the endblades of each stage. The line of division Y-Y between the parts 10 andIf is thus displaced from the diametral line X--X at each stage by anamount substantially equal to the amount by which the blade platform I3Iat that stage extends beyond the diametral line. Thus in the arrangementillustrated, the end surfaces of blades [3| of stages 2, 3, 4, 5, 9, i0and if he in the plane of division, that of the first stage liesslightly beyond the plane, and those of the remaining stages lieslightly below the plane of division. The extent by which the endsurfaces project or are set back from the plane of division can howeverbe limited to a maximum of say $0.025 inch.

It will be appreciated from the foregoing description that thisinvention provides a construction of stator-blade and stator-casingwhereby manufacture and assembly of the compressor stator is simplified,and further that the compressor stator is of a strong but lightconstruction and clean external appearance.

The invention is not limited to the construction above set forth. Forexample if desired the blade platform may be provided as illustrated inFigure '7 in which the same references as previously used are employedto indicate corresponding parts, with a pair of outwardlydirected,axially-spaced, curved surfaces 24 intermediate the axially-spaced edgesthereof, for example by being provided with a pair of radially extendingribs 23, to co-operate with corresponding inwardly-directed curvedsurfaces !9 formed internally of the wall M of the casing, for exampleby providing thereon a pair of webs such as 'webs 16 between each pairof webs l5.

We claim:

1. An axial-flow compressor stator assembly comprising a stator casinghaving a relatively thin Wall, a plurality of axially-spaced maininternal reinforcing webs each main web extending circumferentiallyaround and project ing radially inwardly from the wall and each main webbeing formed with axially-spaced outwardly facing abutment surfacescurved about the axis of said casing, and a plurality of intermediateinternal reinforcing webs there being at least one intermediate webbetween each pair of said main webs, each said intermediate webextending circumferentially around and projecting radially inwardly fromsaid wall and being formed with an inwardly-facing abutment surfacecurved about the axis of said casing; and a plurality of stages ofstator blading, each stage of stator blading comprising a plurality ofblades in circumferential assembly supported and located by a pair ofmain Webs and at least one intermediate web, the blades being formedwith axially and circumferentially extending blade root platforms, whichplatforms are formed each with inwardly-facing abutment surfaces at itsaxially-spaced edges to abut said outwardly-facing abutment surfaces ofthe associated pair of main webs, and each with at least oneoutwardly-facing abutment surface so arranged to cooperate with theinwardly-facing abutment surface of the intermediate web between saidpair of main webs as to maintain the blade root platform in contact withthe abutment surfaces on the main webs and to locate the blade againstradial and rocking movement.

2. An axial-flow compressor stator assembly as claimed in claim 1 inwhich said blade root platforms are formed each on the side thereofremote from the blade with at least one circumferentially and radiallyextending rib having an axial dimension less than the axial dimension ofthe blade root platform, and having at its radially outer end theoutwardly-facing abutment surface which cooperates with theinwardly-facing abutment surface on the intermediate web.

3. An axial-flow compressor stator assembly as claimed in claim 1, inwhich said main reinforcing webs are formed each with axially andcircumferentially extending flanges at their inward ends; said flangesbeing formed at their axially spaced edges with the outwardly-facingabutment surfaces of the main webs, said abutment surfaces having anaxial dimension less than the axial dimension of said flanges.

4. An axial-flow compressor stator assembly as claimed in claim 1,wherein said intermediate reinforcing webs alternate with said mainreinforcing webs.

5. An axial-flow compressor stator assembly tending circumferentiallyaround and projecting radially inwardly from the Wall and each main webbeing formed with axially-spaced outwardlyfacing abutment surfacescurved about the axis of said casing and being formed additionally withinwardly-facing surfaces curved about the axis of the casing toconstitute portions of the outer wall of the working fluid passagethrough the stator casing, and a plurality of intermediate internalreinforcing webs, there being at least one intermediate web between eachpair of said main webs, each said intermediate web extendingcircumferentially around and projecting radially inwardly from said walland being formed with inwardly-facing abutment surface curved about theaxis of said casing; and a plurality of stages of stator bl-ading, eachstage of stator blading comprising a plurality of blades supported andlocated in circumferential assembly by a pair of main webs and at leastone intermediate web, the blades comprising axially andcircumferentially extending root platforms arranged to provide with saidinwardly-facing surfaces of said main webs a substantially smooth outerwall of the working fluid passage through the stator casing, said rootplatforms having each a pair of inwardly-facing abutment surfaces at itsaxially-spaced edges arranged to cooperate with said outwardly-facingabutment surfaces of adjacent main webs and said blade root platformshaving each at least one outwardly-facing abutment surface to abut theinwardly-facing abutment surface of an intermediate web to maintain saidmain webs and said blade root platform in contact thereby to locate theblade against radial and rocking movement, the number ofoutwardly-facing abutment surfaces on each root platform correspondingto the number of intermediate webs between its associated pair of mainwebs.

6. An axial-flow compressor stator assembly as claimed in claim 5 inwhich said blade root platforms are formed each on the side remote fromthe blade with a circumferentially and radially extending rib having anaxial dimension less than the axial dimension of the blade root platformand having at its radially outer end the outwardly-facing abutmentsurface arranged to abut the inwardly-facing abutment surface of anintermediate web between said adjacent main Webs to maintain said mainwebs in contact with said blade root platform and thereby to locate theblade against radial and rocking movement.

'7. An axial-flow compressor assembly as claimed in claim 5, whereinsaid subsidiary reinforcing webs alternate with said main internalreinforcing webs.

8. An axial-flow compressor stator assembly as claimed in claim 5, inwhich the main reinforcing webs are formed with axially andcircumferentially extending flanges at their inward ends, said flangesbeing formed at their axiallyspaced edges with the outwardly-facingabutment surfaces curved about the axis of said casing, said abutmentsurfaces having an axial dimension less than the axial dimension of saidflanges.

9. An axial-flow compressor stator assembly as claimed in claim 8,wherein the pair of axiallyspaced outwardly-facing abutment surfaces areconstituted as circumferential recesses in the thickness of said flangesand wherein the pair of inwardly-facing axially-spaced abutment surfacesof said blade platforms are constituted as recesses in the thickness ofsaid platforms whereby when the blade is mounted in the casing thesurface of the platform facing towards the axis of the casing forms withthe inwardly-facing surfaces of the adjacent main webs a substantiallysmooth outer wall of the working fluid passage through the statorcasing.

CHRISTOPHER AINSWORTH DAVIS.

JOHN HENRY BILL.

FREDERICK WILLIAM WALTON MORLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 735,054 Bentley Aug. 4, 1903868,419 Emmet Oct. 15, 1907 990,321 Westinghouse Apr. 25, 1911 2,220,616Roder 'Nov. 5, 1940 2,240,742 Allen May 6. 1941

